Alternatives to mercury-containing measuring devices

Transcription

1 Alternatives to mercury-containing measuring devices Carsten Lassen and Jakob Maag, COWI A/S Environmental Project No Miljøprojekt

2 The Danish Environmental Protection Agency will, when opportunity offers, publish reports and contributions relating to environmental research and development projects financed via the Danish EPA. Please note that publication does not signify that the contents of the reports necessarily reflect the views of the Danish EPA. The reports are, however, published because the Danish EPA finds that the studies represent a valuable contribution to the debate on environmental policy in Denmark.

3 Table of Content PREFACE 5 SUMMARY AND CONCLUSIONS 7 SAMMENFATNING OG KONKLUSIONER 11 1 INTRODUCTION DEVELOPMENT OF MERCURY CONSUMPTION FOR MEASURING AND CONTROL DEVICES IN DENMARK METHODOLOGY 17 2 THERMOMETERS OTHER THAN FEVER THERMOMETERS APPLICATION OF MERCURY-CONTAINING THERMOMETERS OTHER THAN FEVER THERMOMETERS ALTERNATIVES FOR MAIN APPLICATION AREAS SUMMARY 26 3 MANOMETERS APPLICATION OF MERCURY-CONTAINING MANOMETERS ALTERNATIVES FOR MAIN APPLICATION AREAS SUMMARY 32 4 BAROMETERS APPLICATION OF MERCURY-CONTAINING BAROMETERS ALTERNATIVES FOR MAIN APPLICATION AREAS SUMMARY 35 5 BLOOD PRESSURE MEASURING DEVICES APPLICATION OF MERCURY-CONTAINING BLOOD PRESSURE MEASURING DEVICES ALTERNATIVES FOR MAIN APPLICATION AREAS SUMMARY 41 6 OTHER MERCURY-CONTAINING MEASURING DEVICES 43 REFERENCES 45 ANNEX 1 CONTACTED COMPANIES AND INSTITUTIONS 49 3

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5 Preface Background With the aim of reducing the demand for mercury used in products and speeding up the substitution of mercury, the Extended Impact Assessment for the Community strategy concerning mercury indicated that it would be appropriate to introduce a Community level marketing restriction on mercurycontaining measuring and control equipment for use by the general public and, with some exemptions, in the healthcare sector. The Commission of the European Communities has 24 February 2006 presented a proposal for amending Council Directive 76/769/EEC relating to restrictions on the marketing of certain measuring devices containing mercury. According to the Danish Environmental Protection Agency, the proposed restriction will, as regards fever thermometers and sphygmomanometers, provide a higher level of protection than the existing Danish regulation, whereas the protection level for other devices will be weakened in a lesser extent in Denmark by implementation of the Commission's proposal as indicated in the following table: Devices Danish regulation according to Statutory Order no. 627 of 1 July 2003 The proposal from the Commission Fever thermometers Not prohibited Prohibition Other thermometers Prohibited, except for equipment used for calibration and laboratory use Prohibition of sale to the general public Sphygmomanometers Not prohibited Prohibition of sale to the general public Manometers Barometers Prohibited, except for equipment used for calibration Prohibited, except for equipment used for calibration Prohibition of sale to the general public Prohibition of sale to the general public This study The Danish EPA has launched this study on advantages and drawbacks of alternatives to mercury-containing equipment marketed in Denmark as part of the preparations for the amendment of the directive. The project has been followed by a Steering Group consisting of: Rikke Donchil Holmberg, Danish Environmental Protection Agency Frank Jensen, Danish Environmental Protection Agency Carsten Lassen, COWI A/S Jakob Maag, COWI A/S The report has been prepared by Carsten Lassen and Jakob Maag, COWI A/S. 5

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7 Summary and conclusions The investigation shows that mercury-containing manometers, barometers and thermometers, apart from certain applications in laboratories, have been totally phased out in Denmark and satisfactory, cost-efficient alternatives are available for all identified applications. For blood pressure measurements, mercury-containing sphygmomanometers are still requested by some general medical practitioners and a few hospital departments. In recent years the electronic and mechanical mercuryfree devices have been improved, and devices which are validated with reference to internationally recognised protocols, are marketed at prices corresponding to the price of mercury-containing blood measurement devices. The disadvantage of electronic devices is that they for the user are a kind of "black box", and it is not easily recognisable whether they function correctly, which means that they must be checked more regularly. In spite of this, the electronic devices, which also have significant advantages, supersede mercury-containing devices for most applications concurrently with a significant improvement of the electronic devices and a drop in the price. Electronic equipment has also replaced mercury-containing devices for advanced measurements and calibration of other thermometers, manometers and barometers. Historic consumption of mercury with measuring devices The consumption of mercury for measuring devices in Denmark has during the period from 1982/83 to 2000/01 decreased by a factor of 100 (see table 1). The driving forces behind the decrease have partly been the development of new technologies, in particular the development of electronic devices for automatic measurements, partly been environmental concern which has also resulted in a ban of the marketing of some of the mercury-containing measuring devices. Table 1 Mercury consumption in relation to measuring devices in Denmark Application area Mercury consumption (kg Hg/year) 1982/ / /01 Fever thermometers Other thermometers 1,300-1, Other measuring and control devices including blood measurement devices and mercury for maintenance of existing devices Total 2,480-3, Thermometers other than fever thermometers The marketing of mercury-containing thermometers other than fever thermometers is today banned in Denmark except for marketing of thermometers for calibration of other thermometers and for use in laboratories. 7

8 Alternatives for all original applications of mercury-containing thermometers are available on the market (see table 2). The price of alternatives varies significantly. Liquid-in-glass thermometers are available at the same price as mercury thermometers, whereas the price of some electronic thermometers is up to ten times the price of mercury thermometers. Electronic thermometers are widely used for all applications, because the advantages of the automatic measurements and datalogging compensate for the higher price. Table 2 Marketed alternatives for mercury-containing thermometers in Denmark Application area / product type Marketed alternatives Price of alternatives compared to mercury thermometers Comment Mercury-in-glass thermometers for machines, engines, boilers, etc. Liquid-in-glass thermometer (up to 250 C) Dial thermometers (up to 650 C) same price 2-4 times more Electronic thermome- up to 10 times more Widely used for automatic ters measurements and datalogging Mercury-in-glass thermometers for ambi- Liquid-in-glass ther- same price ent air temperature measurements incl. mometer min/max measurements Electronic thermome- up to 10 times more Used for automatic meas- ters urements, datalogging and standard equipment of weather stations Mercury dial thermometers for remote Dial thermometers 2-4 times more control in the industry and on ships with capillaries with other liquid or gases Electronic thermome- up to 10 times more Widely used for automatic ters measurements and datalogging Mercury-in-glass glass thermometers for Liquid-in-glass ther- same price as ordi- laboratory use mometer (at 1 degree) nary Hg thermometer Electronic thermome- Up to 10 times more Widely used for automatic ters (at 0.1 degree reso- than ordinary Hg ther- measurements and data- lution at a wide tem- mometers logging perature range) same price as certified Hg thermometers The liquid-in-glass thermometers can substitute for mercury-in-glass thermometers for most applications except for measurements in the temperature range above 250 C and for measurements in laboratories at less than 1 centigrade resolution. For high-temperature applications in the industry, the mercury thermometers are typically replaced by dial thermometers for manual reading or by electronic thermometers. For high-resolution measurements the mercury thermometers are to some extent replaced by electronic thermome- 8

9 ters, but the mercury thermometers are still widely used in laboratories, e.g. for temperature measurements in synthesis baths. A barrier for phasing out mercury thermometers in laboratories is that the use of mercury thermometers is prescribed by some standards used in the laboratories. Development of revised standards would encourage mercury substitution in the laboratory sector. Barometers Electronic barometers for automatic measurements of barometric pressure have in Denmark totally replaced mercury barometers for professional use in weather stations, airports, etc. Electronic barometers are also used for calibration of other barometers. The electronic barometers are as precise as the mercury barometers and have the advantage of automatic data logging. As mercury barometers have not been marketed in Denmark for many years, a price comparison has not been possible, but a study from the USA concludes that aneroid (mechanical liquid free) and electronic barometers are cost effective alternatives. Even though the electronic barometers may be more expensive than mercury thermometers, the lower price of mercury barometers would most probably not be a decisive property for the main part of the professional users. If available at significantly lower prices, the mercury barometers could perhaps be reintroduced for a few applications, where automatic reading is not requested. Blood pressure measuring devices The use of mercury sphygmomanometers for blood pressure measurements are not prohibited in Denmark. Mercury sphygmomanometers are still requested by some general medical practitioners and to a small extent by some hospital departments. For use by the general public for measurements in the home, semi-automatic electronic devices has totally replaced mercury sphygmomanometers. In hospitals, mercury sphygmomanometers have nearly 100% been replaced by aneroid (liquid-free) manual sphygmomanometers or electronic semiautomatic and automatic devices. The difference between the application patters in hospitals and by the general medical practitioners is partly that in hospitals use more advanced and expensive electronic equipment, partly that the hospitals have technical departments responsible for the maintenance of the equipment. Mercury-free devices, validated with reference to the protocols of the British Hypertension Society or the International Society of Hypertension are available at approximately the same price as mercury sphygmomanometers. The use of mercury-containing strain gauges, and alternatives to these devices, has not been investigated; reference is made to a recent Swedish study. Other measuring devices Mercury has previously, and to a small extent, been used in other types of measuring devices. The marketing of such devices in Denmark has been banned for some years. The alternatives marketed today have not been investigated in this project. There are no current exemptions to the Danish ban. 9

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11 Sammenfatning og konklusioner Undersøgelsen viser at kviksølvholdige manometre, barometre og termometre, bortset fra visse anvendelser af termometre i laboratorier, er helt udfaset i Danmark og at der findes tilfredsstillende, omkostningseffektive alternativer til alle identificerede formål. Til blodtryksmåling efterspørges kviksølvholdige apparater stadig af nogle praktiserende læger og få hospitalsafdelinger. I de senere år er der sket en forbedring af de elektroniske og mekaniske kviksølvfrie blodtryksmålere, og en række forskellige apparater, som er godkendt efter anerkendte internationale protokoller, forhandles til priser svarende til prisen på kviksølvholdige blodtryksmålere. Det elektroniske udstyr har den ulempe at det for brugeren fungerer som en "sort boks", og at det ikke er umiddelbart nemt at se om det fungerer korrekt, hvilket indebærer at det skal kontrolleres oftere. På trods af disse ulemper fortrænger det elektroniske udstyr, som også har en række væsentlige fordele, manuelt udstyr i takt med at det elektroniske udstyr forbedres, og prisen på udstyret falder. Til avancerede målinger og kalibrering af andre termometre, manometre og barometre anvendes der i dag stort set kun elektronisk apparatur. Baggrund EU Kommissionen har den 24. februar 2006 udsendt et forslag til en ændring af Rådets direktiv 76/769/EØF med henblik på at begrænse markedsføringen af kviksølvholdige måleinstrumenter i EU. Med forslaget vil det generelle beskyttelsesniveau i EU på dette område forbedres. På visse punkter vil forslaget imidlertid kunne indebære at beskyttelsesniveauet i Danmark forringes i mindre grad, da de danske regler for nogle typer af måle- og kontroludstyr er mere restriktive end Kommissionens forslag. I den følgende tabel er vist forskellen mellem de eksisterende danske regler og Kommissionens forslag. Måleudstyr Danske regler Kommissionens forslag Lægetermometre Ikke forbud Forbud Andre termometre Forbud undtagen til kalibrering og analyse-formål Forbud mod salg til private Blodtryksmålere Ikke forbud Forbud mod salg til private Manometre Barometre Forbud undtagen til kalibrering Forbud undtagen til kalibrering Forbud mod salg til private Forbud mod salg til private Miljøstyrelsen har igangsat denne undersøgelse med henblik på at belyse, hvilke alternativer til kviksølvholdigt måleudstyr der i dag anvendes i Danmark, og i hvilken grad en ændring af reglerne vil kunne indebære at kviksølvholdigt udstyr kommer tilbage på det danske marked. Undersøgelsen Undersøgelsen bygger på oplysninger indhentet fra danske leverandører af 11

12 måleudstyr samt vurderinger fra danske eksperter i måling med det pågældende udstyr. Historisk forbrug af kviksølv med måleudstyr Forbruget af kviksølv med måleudstyr i Danmark er i perioden 1982/83 til 2000/01 faldet med en faktor hundrede (se tabel 1). Årsagen til denne udvikling har dels været udviklingen af nye teknologier, især udviklingen af elektronisk udstyr til automatiske malinger, dels været miljøhensyn, som også har udmøntet sig i det eksisterende forbud mod markedsføring af kviksølvholdigt måleudstyr til de fleste ikke-medicinske anvendelser. Tabel 0.1 Kviksølvforbrug i relation til brugen af måleudstyr i Danmark Produktgruppe Kviksølvforbrug (kg Hg/år) 1982/ / /01 Lægetermometre Andre termometre 1,300-1, Andet måleudstyr inklusive blodtryksmålere og kviksølv solgt til vedligeholdelse af måleudstyr I alt 2,480-3, Andre termometre end lægetermometre Markedsføring af kviksølvholdige andre termometre end lægetermometre er i dag forbudt i Danmark med undtagelse af termometre, som bruges til at kalibrere andre termometre eller bruges til laboratorieformål. Alternativer, som kan erstatte kviksølvholdige termometre til alle anvendelser, er i dag tilgængelige på markedet (se tabel 2). Prisen på alternativer varierer betydeligt. Kviksølvfrie væske-i-glas termometre fås til omtrent samme pris som kviksølvtermometre, mens prisen for elektroniske termometre kan være op til 10 gange højere. På trods af den højere pris sælges de elektroniske termometre i stor udstrækning til alle typer anvendelser, idet fordelene ved at kunne lave automatiske målinger opvejer den højere pris. Glastermometre med andre væsker kan erstatte kviksølvholdige glastermometre til de fleste anvendelser bortset fra målinger i temperaturområdet over 250 C samt målinger i laboratorier med en målenøjagtighed på mindre end 1 grad Celsius. For målinger ved temperaturer over 250 C i industrien anvendes typisk skivetermometre for manuel aflæsning eller elektroniske termometre for automatiske målinger. Til målinger med høj nøjagtighed er kviksølv til en vis grad erstattet af elektroniske termometre, men kviksølvtermometre har stadig en udbredt anvendelse i laboratorier, fx for temperaturmåling i syntesebade. En barriere for at udfase kviksølvtermometre til laboratorieformål er at brugen af kviksølvtermometre foreskrives i visse analysestandarder, som følges i laboratorierne. 12

13 Tabel 2 Markedsførte alternativer til kviksølvholdige termometre. Anvendelsesområde / produkttype Markedsførte alternati- Pris på alternativer Kommentar ver sammenlignet med kviksølvholdige termometre Kviksølvholdige glastermometre til brug i Væske-i-glas termo- samme pris Har erstattet kviksølvter- på maskiner, motorer, kedler og lignende metre (op til 250 C) mometre til målinger op til 250 C Skivetermometre (op til 2-4 gange mere Har erstattet kviksølvter- 650 C) mometre ved målinger over 250 C, fx i udstødning Elektroniske termomet- op til 10 gange mere Vidt udbredt til automati- re ske målinger Kviksølvholdige glastermometre til måling Væske-i-glas termo- samme pris Bruges i en vis grad i ter- af temperatur i omgivende luft inkl. metre (op til 250 C) mometre til at vise rum- min/max målinger temperatur Elektroniske termomet- op til 10 gange mere Bruges til automatiske re målinger og er standardudstyr i vejrstationer Kviksølvholdige skivetermometre til fjern- Skivetermometre med 2-4 gange mere Bruges til manuelle fjernaf- aflæsning af temperaturen i industrien og kapillarer med andre læsninger på skibe væsker eller luftarter Elektroniske termomet- op til 10 gange mere Vidt udbredt til automati- re ske målinger Kviksølvholdige glastermometre til brug i Væske-i-glas termo- samme pris Anvendes bredt til alle laboratorier metre (målinger med 1 formål, hvor der ikke er grads nøjagtighed) behov for større end 1 grads målenøjagtighed Elektroniske termomet- Op til 10 gange mere Vidt udbredt til automati- re (med 0.1 grads nøj- end ordinære Hg ter- ske målinger og målinger agtighed inden for et mometre med stor nøjagtighed bredt temperaturinter- samme pris som val) certificerede Hg thermometre Manometre Forud for det nuværende forbud udgjorde kviksølvmanometre af U-rørs typen kun nogle få procent af det danske marked for manometre. Kviksølvmanometre blev anvendt til målinger ved relativt lave tryk, især inden for VVS branchen, fx i forbindelse med service på oliefyr, men kunne også bruges på enkelte maskiner. Kviksølvmanometrene har uden større vanskelighed kunnet erstattes af andre typer manometre. Alternativerne er enten mekaniske fjedermanometre til manuel aflæsning eller elektroniske manometre med digital skærm og mulighed for dataopsamling. Til kalibrering af andet udstyr bruges også elektroniske manometre. 13

14 Ifølge de kontaktede leverandører fås de mekaniske fjedermanometre til priser, som varierer fra mindre end til omtrent samme pris som et kviksølvmanometer, mens prisen på de elektroniske manometre er 3-4 gange prisen på et kviksølvmanometer. De elektroniske har dog nogle væsentlige fortrin frem for de manuelle kviksølvmanometre, som opvejer den højere pris og er vidt udbredte. Ifølge leverandører er det meget usandsynligt at kviksølvmanometre vil blive genindført til nogen anvendelse i Danmark. Barometre Elektroniske barometre til automatisk måling af barometrisk tryk har i Danmark fuldstændig erstattet kviksølvbarometre til professionelt brug i vejrstation, lufthavne, m.m. Elektroniske barometre bruges også til kalibrering af andre barometre. De elektroniske barometre er lige så præcise som kviksølvbarometre og har den fordel at de kan udføre automatisk dataopsamling. Da kviksølvbarometre til professionelle formål ikke har været markedsført i Danmark i mange år, har det ikke været muligt at foretage en prissammenligning, men en undersøgelse fra USA konkluderer at aneroide barometre (mekaniske, væskefrie barometre) og elektroniske barometre er omkostningseffektive alternativer til kviksølvbarometre. Også selv om elektroniske barometre er dyrere end kviksølvbarometre, vil den lavere pris af kviksølvbarometre ikke være af afgørende betydning for flertallet af de professionelle brugere. Der vil muligvis være en begrænset efterspørgsel efter kviksølvbarometre til enkelte anvendelser, hvor der ikke er behov for automatiske målinger, hvis disse barometre kan leveres til væsentligt lavere priser end de automatiske. Blodtryksmålingsudstyr Det er i dag tilladt at bruge kviksølvholdigt udstyr til blodtryksmåling i Danmark. Blodtryksmålere med kviksølvmanometre (såkaldte sphygmomanometre) efterspørges stadig af nogle praktiserende læger og i en meget lille grad af visse hospitalsafdelinger. Til blodtryksmåling i hjemmet har automatiske elektroniske blodtryksmålere helt erstattet kviksølvmanometre, og Dansk Hypertensionsselskab, som er den lægefaglige ekspertise på dette område, anbefaler i dag at der til hjemme- og døgnblodtryksmåling udelukkende anvendes automatiske apparater. På hospitalerne er kviksølvmanometre næsten 100 % erstattet af elektronisk udstyr eller aneroide (dvs. mekaniske væskefrie) manuelle blodtryksmålere. Årsagen til de forskellige brugsmønstre hos hospitaler og de praktiserende læger er dels at der på hospitalerne anvendes mere avanceret og dyrere elektronisk udstyr, dels at hospitalerne har tekniske afdelinger som varetager vedligeholdelsen af udstyret. Dansk Hypertensionsselskab angiver i deres seneste anbefaling at moderne aneroidmanometre er helt på højde med kviksølvmanometre, hvis de vedligeholdes regelmæssigt. Forskellige typer af kviksølvfrie apparater, som er godkendt i henhold til testprotokoller udarbejdet af British Hypertension Society eller International Society of Hypertension kan fås til omtrent den samme pris som kviksølvmanometre. Brugen af kviksølvholdige strækfølere (strain gauges), og alternativer til dette udstyr, er ikke blevet undersøgt, men læsere henvises til en ny svensk undersøgelse. 14

15 Andet måleudstyr Kviksølv har tidligere i mindre grad været brugt i andre typer af måleudstyr. Markedsføring af sådant udstyr har i en årrække ikke været tilladt i Danmark til andet end kalibreringsformål, men det er ikke nærmere undersøgt, hvilke alternativer der i dag markedsføres. Der er for øjeblikket ikke givet nogle dispensationer til brug af kviksølv til andet måleudstyr. 15

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17 1 Introduction The present study presents information on alternatives to mercury-containing non-fever thermometers, barometers, manometers and blood pressure measuring devices marketed for professional use in Denmark. The four groups of devices are selected because mercury until recently has been used or is still used in Denmark for some types of these devices. Besides the concerned applications, mercury may to a minor extent be used for other non-electrical or non-electronic measuring and control devices. Those devises are briefly described in Chapter Development of mercury consumption for measuring and control devices in Denmark The development in the consumption of mercury for measuring devices during the period 1982/83 to 2000/01 is shown in table 1.1. During this period the total consumption of mercury for these application areas decreased nearly 100 times. The figures present the total mercury content of measuring devices sold in the years given in the table as well as mercury sold for maintenance of existing devices (relevant to "other measuring and control devices"). It is notable that the total consumption of non-fever thermometers in both 1982/83 and 1992/93 was about twice the consumption of fever thermometers. Similar results have been reported from the UK using figures from around 2000 (Floyd et al. 2002). Table 1.1 Mercury consumption in relation to measuring devices in Denmark (Skårup et al. 2004) Application area Mercury consumption (kg Hg/year) 1982/ / /01 Fever thermometers Other thermometers 1,300-1, Other measuring and control devices including manometers, barometers, blood measuring devices and mercury for maintenance of existing devices Total 2,480-3, ,1 1.2 Methodology Thermometers, barometers and manometers The marketing of mercury-containing thermometers (apart from fever thermometers and thermometers used in laboratories) manometers and barometers is banned in Denmark today. In order to describe the alternatives, which have substituted the formerly used mercury-containing devices, suppliers of relevant equipment have been contacted. Furthermore, research institutions using the most advanced devices for calibration of other devices, have been 17

18 contacted in order to obtain independent statements on the advantages and drawbacks of alternatives. Blood pressure measuring devices Mercury-containing blood pressure devices are to some extent used in the medical sector in Denmark today. Alternatives to the mercury-containing devices have recently been described in a Swedish study, which also describes the Swedish experience in replacing the mercury-containing devices (Kemi & Miljø Konsulenterne AB 2005). The major discussion concerning the use of alternatives in Denmark relates to the reliability and stability of the equipment in the actual use situation, in particular by the general medical practitioners. In order to supplement the information in the Swedish study with Danish experience, Danish suppliers of blood measuring devices have been contacted in order to investigate to what extent and by whom mercury-containing bloodpressure devices are purchased today. Furthermore, information on marketed alternatives to mercury-containing blood pressure measuring devices has been collected. Examples of marketed equipment In order to illustrate some alternatives to mercury-containing devices, some examples of devices marketed in Denmark are shown in this report. For each example a supplier, from which the information is obtained, is indicated. The equipment may quite likely also be supplied by other companies in Denmark. 18

19 2 Thermometers other than fever thermometers 2.1 Application of mercury-containing thermometers other than fever thermometers Thermometers measure temperature. Apart from fever thermometers, three types of mercury-containing thermometers were previously used in Denmark: Mercury-in-glass thermometers; Mechanical mercury thermometers with a dial for remote control; Contact thermometers (electric thermostats). In Denmark, the use of thermometers other than fever thermometers is only allowed for calibration purposes and for laboratory use. Mercury thermometers may in principle be used for all types of temperature measuring for manual reading in the temperature interval above the freezing point of mercury, -39 C. The most common mercury thermometers consist of mercury encased in a thin glass tube that rises and falls with temperature. This thermometer was widely used in laboratories, as room thermometers and for temperature monitoring of machines, combustion processes and industrial processes. These types of thermometers are still allowed and marketed for use in laboratories. The mercury content was g Hg/piece for large thermometers for boilers, whereas smaller thermometers contained 4-5 g Hg/piece (Hansen 1985). Thermometers used today in laboratories typically contain about 14 g Hg/piece corresponding to 1 ml mercury. Another type, previously used for remote control of large engines or combustion processes, consists of a sensor on the machine, an up to 40 m long mercury filled capillary connecting the sensor and the control room and a gauge consisting of a bourdon coil with a pen or needle for reading the temperature (Rasmussen 1992). The mercury content ranged from about 5 to 200 g (Maag et al. 1996). These thermometers were mainly used for marine engine purposes and within the power sector. Mercury-containing contact thermometers, in fact thermostats, were previously used for switching of a heating element in laboratories (Rasmussen 1992). When the mercury expanded in response to increased temperature, it established an electric contact between two terminals. The thermostats are electric equipment and not within the scope of the current study. A thermometer with a U-shaped tube can be used for min/max thermometers indicating minimum and maximum temperature during a period of time. Mercury-containing min/max thermometers were previously part of the equipment of type of small weather stations called "English huts" [Danish: 19

20 engelsk hytte], but they have today been replaced by electronic thermometers (Dahl 2006). For long transports in e.g. refrigerated containers, insurance companies demand continuous monitoring and verification of the temperature during the whole transport (Gustafsson 1997). According to a Swedish study, in the late 1990s a manually supervised instrument containing 190 g mercury dominated the market for marine transports. The use of such instruments has not been described in Danish studies, but it may have been used. Today, automatic devices without mercury, approved by the international insurance companies for supervision of refrigerated containers, are marketed. Some standards, e.g. some German DIN standards, prescribe the use of mercury thermometers, which may be a hindrance for phasing out mercury thermometers for laboratory use. Development of revised standards would encourage mercury substitution in the laboratory sector. Advantages and drawbacks of the mercury-containing equipment - Laboratory thermometers Mercury thermometers used in laboratories are exempted from the Danish ban. The advantage of the mercury thermometers is that they are stable and easy to apply, and that it is immediately recognisable, when they are broken and do not function. Compared with glass thermometers filled with other liquids, the mercurycontaining thermometers are more precise and are the only suitable liquid thermometers for measurements at 0.1 degree resolution according to Andersen (2006). Thermometers tested and certified for accurate measurements at 0.1 degree resolution are marketed at prices of about ten times the price of ordinary mercury thermometers (Thoft 2006). The disadvantage of the mercury thermometers is that the thermometers easily brake and that the toxic mercury may be spread to the laboratory environment and surroundings at the breakage. Further, by heating of the thermometers, small bubbles may be formed in the mercury column resulting in a wrong reading of the temperature. The available electronic thermometers are generally more accurate than mercury-containing thermometers, if properly calibrated. The laboratories accredited for calibration of thermometers typically use platinum resistance thermometers for calibrating other thermometers. According to Andersen (2006) from the thermometry laboratory of the Risø National Laboratory, an essential disadvantage of the electronic thermometers by normal laboratory use is that there is no visible indication, if the probe is damaged, e.g. after a drop of the thermometer onto the floor. Contrary to this, Nielsen (2006) from the national temperature reference laboratory of the Danish Technological Institute does not find any justification for the continued use of mercury thermometers in laboratories. The electronic thermometers are more accurate than the mercury-containing thermometers, but have to be calibrated more often. The electronic thermometers are typically calibrated every year, whereas mercury thermometers are typically calibrated every second year. When using the electronic thermometers it is necessary to check and recalibrate the thermometer, when it has been dropped. Nielsen (2006) finds this to be a relatively simple task compared to the clean up, when a mercury-containing thermometer is dropped. 20